Mutualistic relationship between Nitrospira and concomitant heterotrophs.

Nitrifying chemoautotrophs support the growth of diverse concomitant heterotrophs in natural or engineered environments by supplying organic compounds. In this study, we aimed to investigate this microbial association, especially (i) to distinguish whether the relationship between nitrifying chemoautotrophs and heterotrophs is commensal or mutualistic, and (ii) to clarify how heterotrophs promote the growth of autotrophic nitrite-oxidizing bacteria (Nitrospira). Pure cultured Nitrospira (Nitrospira sp. ND1) was employed in this study. Heterotrophs growing with metabolic by-products of Nitrospira as a sole carbon source were isolated from several environmental samples and used to test the growth-promoting activity of Nitrospira. Furthermore, liquid chromatography-mass spectrometry analysis was conducted to evaluate how heterotrophs consumed chemical compounds produced by Nitrospira and newly produced during co-cultivation. Notably, Nitrospira growth was stimulated by co-cultivation with some heterotrophs and the addition of spent media of some strains, suggesting that not only heterotrophs but also Nitrospira received benefits from their mutual co-existence. Furthermore, the data suggested that some of the growth-promoting heterotrophs provided as-yet-unidentified growth-promoting factors to Nitrospira. Overall, Nitrospira and heterotrophs thus appear to exhibit a mutualistic relationship. Such mutualistic relationships between autotrophs and heterotrophs would contribute to the stability and diversity of microbial ecosystems.

Triggering Growth via Growth Initiation Factors in Nature: A Putative Mechanism for in situ Cultivation of Previously Uncultivated Microorganisms.

Most microorganisms resist cultivation under standard laboratory conditions. On the other hand, cultivating microbes in a membrane-bound device incubated in nature (in situ cultivation) can be an effective approach to overcome this limitation. In the present study, we applied in situ cultivation to isolate diverse previously uncultivated marine sponge-associated microbes and comparatively analyzed this method's efficiencies with those of the conventional method. Then, we attempted to investigate the key and previously unidentified mechanism of growing uncultivated microorganisms by in situ cultivation focusing on growth triggering via growth initiation factor. Significantly more novel and diverse microbial types were isolated via in situ cultivation than by standard direct plating (SDP). We hypothesized that some of environmental microorganisms which resist cultivation are in a non-growing state and require growth initiation factors for the recovery and that these can be provided from the environment (in this study from marine sponge). According to the hypothesis, the effect of the sponge extract on recovery on agar medium was compared between strains derived from in situ and SDP cultivation. Adding small amounts of the sponge extracts to the medium elevated the colony-formation efficiencies of the in situ strains at the starvation recovery step, while it showed no positive effect on that of SDP strains. Conversely, specific growth rates or saturated cell densities of all tested strains were not positively affected. These results indicate that, (1) the sponge extract contains chemical compounds that facilitate recovery of non-growing microbes, (2) these substances worked on the in situ strains, and (3) growth initiation factor in the sponge extract did not continuously promote growth activity but worked as triggers for regrowth (resuscitation from non-growing state).

Peptide precursors that acquire denatured collagen-hybridizing ability by O-to-N acyl migration at physiological pH.

Here, we report peptide probes with either single or cyclic double stranded collagen-like sequences that spontaneously acquire collagen-hybridizing ability at physiological pH. These peptides have ester bonds derived from O-acyl isopeptide units that are converted to amide bonds via intramolecular O-to-N acyl migration by a pH shift. The peptides that do not require pre-treatment for disassembly will be useful as prodrugs in theranostic treatments targeting unfolded collagen.

Sameuramide A, a new cyclic depsipeptide isolated from an ascidian of the family Didemnidae.

Sameuramide A (1), a new cyclic depsipeptide encompassing one each of alanine, N-methyl alanine, N-methyl dehydroalanine, N,O-dimethyl threonine, phenyllactic acid, three ß-hydroxy leucines, and two propionates, was isolated from a didemnid ascidian collected at the northern part of Japan. The planar structure was established based on the interpretation of MS and NMR data. The absolute configuration of the subunits was determined by the advanced Marfey's method and the chiral LC-MS analysis. Compound 1 exhibited the activity of maintaining colony formation of murine embryonic stem (mES) cells without leukemia inhibitory factor (LIF). Down regulation of the gene expression of Krüppel-like transcription factor 4 (Klf4) indicated that 1 itself was not able to maintain the undifferentiated state of the mES cells. However, the expression levels of the marker genes (Nestin, T, Sox17) for three germ layers were upregulated in embryoid bodies (EBs) after treatment of 1 together with LIF, suggesting that 1 plays a supportive role for LIF in maintaining the multipotency of mES cells.

Cinanthrenol A, an estrogenic steroid containing phenanthrene nucleus, from a marine sponge Cinachyrella sp.

Cinanthrenol A (1), a new steroid composed of a phenanthrene and a spiro[2,4]heptane system, was isolated from the marine sponge Cinachyrella sp. It is the first phenathrene-containing steroid with estrogen activity.